Chemistry Reference
In-Depth Information
O
OH
1.
2. K
2
CO
3
, MeOH
Li
SiMe
3
CO
2
Me
CO
2
Me
7.91
7.92
OH
SH
BF
3.
OEt
2
(OC)
6
Co
2
(OC)
6
Co
2
CO
2
Me
CO
2
Me
7.93
7.94
H
Δ
S
O
S
(OC)
6
Co
2
CO
2
Me
7
5
7
.
9
CO
2
Me
H
H
CuI, DIBAL
LiOH
O
S
O
S
H
H
CO
2
Me
7.97
CO
2
H
7.98
Scheme 7.25
cobalt complex
7.88
with good diastereoselectivity. The subsequent Pauson-Khand reaction then appended
two five-membered rings.
A similar Nicolas-Pauson-Khand combination was used in a synthesis of the ketone analogue of biotin
7.98
, required for biochemical studies (Scheme 7.25).
48
In this case, the Nicholas reaction was intermolecular,
between allyl thiol as the nucleophile and carbocation
7.94
generated from alcohol
7.93
. The Pauson-Khand
reaction was then between the dicobalt complexed alkyne
7.95
and the double bond from the thiol moi-
ety. The Pauson-Khand reaction proceeded with no stereoselectivity, and the diastereoisomers had to be
chromatographically separated at a later stage. The synthesis was completed by reduction of the alkene of
cyclopentenone
7.96
, without using palladium-catalysed hydrogenation due to the sulfide moiety, and ester
hydrolysis.
References
1. Iron also forms complexes of this type (Cotton, F. A.; Jamerson, J. D.; Stults, B. R.
J. Organomet. Chem.
1975
,
94
,
C53), but they have attracted little interest from synthetic organic chemists.
2. (a)Sly,W.G.
J. Am. Chem. Soc.
1959
,
81
, 18; (b) Cotton, F. A.; Jamerson, J. D.
etal.J.Am.Chem.Soc.
1976
,
98
,
1774.
3. Isobe, M.; Hosokawa, S.
et al. Chem. Lett.
1996
, 473.
4. Najdi, S. D.; Olmstaed, M. M.
et al. J. Organomet. Chem.
1992
,
431
, 335.
5. (a) Ju, J.; Reddy
etal.J.Org.Chem.
1989
,
54
, 5426; (b) Mukai, C.; Suzuki, K.
et al. J. Chem. Soc., Perkin Trans I
1992
, 141; (c) Caddick, S.; Delissar, V. M.
et al. Tetrahedron
1999
,
55
, 2737; for the reaction with allyl boranes, see
(d) Ganesh, P.; Nicholas, K. M.
J. Org. Chem.
1997
,
62,
1737.
6. Jiang, Y.; Ichikawa, Y.; Isobe, M.
Tetrahedron
1997
,
53
, 5103.
7. Hosokawa, S.; Isobe, M.
Tetrahedron Lett.
1998
,
39
, 2609.
8. Takai, S.; Ploypradith, P.
et al. Synlett
2002
, 588.
